AVRO外部表

前提条件

• 已具备访问OSS的权限。阿里云账号（主账号）、RAM用户或RAMRole身份可以访问OSS外部表，授权信息请参见OSS的STS模式授权。

• （可选）已准备好OSS存储空间（Bucket）、OSS目录及OSS数据文件。具体操作请参见创建存储空间、管理目录和简单上传。

  MaxCompute已支持在OSS侧自动创建目录，对于携带外部表及UDF的SQL语句，您可以通过一条SQL语句执行读写外部表及UDF的操作。原手动创建目录方式仍然支持。

• 已创建MaxCompute项目。具体操作请参见创建MaxCompute项目。

  由于MaxCompute只在部分地域部署，跨地域的数据连通性可能存在问题，因此建议Bucket与MaxCompute项目所在地域保持一致。

• 已具备在MaxCompute项目中创建表（CreateTable）的权限。表操作的权限信息请参见MaxCompute权限。

使用限制

• OSS外部表不支持cluster属性。

• 单个文件大小不能超过3 GB，如果文件过大，建议拆分。

数据类型支持

MaxCompute数据类型详情请参见1.0数据类型版本、2.0数据类型版本。

创建外部表

CREATE EXTERNAL TABLE <mc_oss_extable_name>
(
  <col_name> <data_type>,
  ...
)
[COMMENT <table_comment>]
[PARTITIONED BY (<col_name> <data_type>, ...)]
STORED AS avro
LOCATION '<oss_location>';

写入数据

MaxCompute写入数据至OSS的语法，详情请参见将数据写入OSS。

查询分析

• SELECT语法，详情请参见读取OSS数据。

• 优化查询计划，详情请参见查询优化。

使用示例

通过内置开源数据解析器创建AVRO格式外部表并将数据写入OSS进行查询。

1. 准备数据。

   登录OSS控制台，上传测试数据20250612TableSink至OSSBucket指定目录external-table-test/avro/dt=20250521/。具体操作请参见OSS文件上传。

2. 创建AVRO格式外部表。

   CREATE EXTERNAL TABLE mc_oss_extable_name_avro_pt 
   (
     vehicleId STRING,
     recordId STRING,
     patientId STRING,
     calls STRING,
     locationLatitute STRING,
     locationLongtitue STRING,
     recordTime STRING,
     direction STRING
   ) 
   PARTITIONED BY (dt STRING) 
   STORED AS avro 
   LOCATION 'oss://oss-cn-hangzhou-internal.aliyuncs.com/external-table-test/avro/';
   
   --引入分区数据。
   MSCK REPAIR TABLE mc_oss_extable_name_avro_pt ADD PARTITIONS;

3. 读取AVRO外部表。

   SELECT * FROM mc_oss_extable_name_avro_pt WHERE dt=20250521;

   返回结果如下：

   +------------+------------+------------+------------+------------------+-------------------+------------+------------+------------+
   | vehicleid  | recordid   | patientid  | calls      | locationlatitute | locationlongtitue | recordtime | direction  | dt         |
   +------------+------------+------------+------------+------------------+-------------------+------------+------------+------------+
   | 1          | 12         | 76         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:10 | SW         | 20250521   |
   | 1          | 1          | 51         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:00 | S          | 20250521   |
   | 1          | 2          | 13         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:01 | NE         | 20250521   |
   | 1          | 3          | 48         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:02 | NE         | 20250521   |
   | 1          | 4          | 30         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:03 | W          | 20250521   |
   | 1          | 5          | 47         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:04 | S          | 20250521   |
   | 1          | 6          | 9          | 1          | 46.81006         | -92.08174         | 9/14/2014 0:05 | S          | 20250521   |
   | 1          | 7          | 53         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:06 | N          | 20250521   |
   | 1          | 8          | 63         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:07 | SW         | 20250521   |
   | 1          | 9          | 4          | 1          | 46.81006         | -92.08174         | 9/14/2014 0:08 | NE         | 20250521   |
   | 1          | 10         | 31         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:09 | N          | 20250521   |
   +------------+------------+------------+------------+------------------+-------------------+------------+------------+------------+

4. 写入AVRO外部表。

   INSERT INTO mc_oss_extable_name_avro_pt PARTITION (dt='20250521') VALUES ('1','16','76','1','46.81006','-92.08174','9/14/2014 0:10','SW');

5. 查询写入数据。

   SELECT * FROM mc_oss_extable_name_avro_pt WHERE dt=20250521;

   返回结果如下：

   +------------+------------+------------+------------+------------------+-------------------+------------+------------+------------+
   | vehicleid  | recordid   | patientid  | calls      | locationlatitute | locationlongtitue | recordtime | direction  | dt         |
   +------------+------------+------------+------------+------------------+-------------------+------------+------------+------------+
   | 1          | 16         | 76         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:10 | SW         | 20250521   |
   | 1          | 12         | 76         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:10 | SW         | 20250521   |
   | 1          | 1          | 51         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:00 | S          | 20250521   |
   | 1          | 2          | 13         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:01 | NE         | 20250521   |
   | 1          | 3          | 48         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:02 | NE         | 20250521   |
   | 1          | 4          | 30         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:03 | W          | 20250521   |
   | 1          | 5          | 47         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:04 | S          | 20250521   |
   | 1          | 6          | 9          | 1          | 46.81006         | -92.08174         | 9/14/2014 0:05 | S          | 20250521   |
   | 1          | 7          | 53         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:06 | N          | 20250521   |
   | 1          | 8          | 63         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:07 | SW         | 20250521   |
   | 1          | 9          | 4          | 1          | 46.81006         | -92.08174         | 9/14/2014 0:08 | NE         | 20250521   |
   | 1          | 10         | 31         | 1          | 46.81006         | -92.08174         | 9/14/2014 0:09 | N          | 20250521   |
   +------------+------------+------------+------------+------------------+-------------------+------------+------------+------------+